Stuck hex bolt in rear brake caliper

[Nails]

On the 99 AE there is a hex backing screw under a cover screw used to adjust the rear brake piston. Seems this one doesn't want to move and I don't want to round the hex surface over torquing.

I am guessing the size is a 4 and to back it out, to move the piston in, I turn it counter-clockwise if I were looking directly at the head. Is that right or am I trying to turn the wrong way? It's not reverse threaded is it?

Any ideas? Right now I have liquid wrench soaking on it as I type this.

Thanks

[trickyrix]

The piston may be stuck. That hex "screw" isn't really a screw, but an adjuster that's geared to the piston. Turn it counter-clockwise to retract the piston. You might try wiggling the piston with channel locks (don't scratch the piston - use a shop towel to protect it) or tapping it with a mallet to see if it's cocked in the bore (boy, that sounds weird). Anyhow, hope that helps... also, be careful that you don't lose the adjuster - they're not really held in so they can fall out if the you turn the caliber on it's back.

Of course, it could be that the piston is already retracted all the way back into the caliper.

[Nails]

Excellent info, thanks Trickrix! I've finished bleeding the rears and put the tires back on. Billy's here now so I'm done for today. I'll try it again tomorrow. Even if I can't get it she'll be ok for Hallett with new fluid and the rears are at least 3/4s full thickness.

[trickyrix]

No problemo... we can take a look at it tomorrow night and make sure that brake's not dragging. It's probably fine since the pads are good, but that hex should spin very easily - strange...

[sammm]

Be sure to lube up the caliper slider pins while you're in there.

[Walsted]

On a friend's NA, (similar, if not the same,) I had a similar problem which turned out to be dirt in the mechanism. I didn't really know what I was doing at the time, but the adjuster wouldn't back out for the new pads - it was stuck in place. I sprayed a can of PB Blaster in the hole for the adjustment, and the adjuster fell out with a grain sized rock in the teeth. I have no idea how it got into the closed system, since I was doing post-purchase maintenance, but removing the debris made it a LOT easier to adust.

Hope this helps

[POS Racing]

Walsted may be onto something with dirt, I had a similar problem with the wifes NB, brake cleaner got it loose. YMMV

Good pictures showing the rear calipers here - http://www.miata.net/garage/ebrake/index.html

[Nails]

Thanks for all the suggestions. I got some PB cleaner after my brake cleaner didn't get it loosened. I also bought some hex wrenches that would allow me to get some more torque on it. Finally after several soakings it came free but I think I'll need a new one.


I'm guessing I should get another caliper too now?

[trickyrix]

I'd say there's a good chance that the mechanism inside the caliper is hosed, so you probably need a new caliper.

Looks like the one from NAPA is about the cheapest.

[Nails]

Got a new caliper from O'reilly's today for about 67 bucks. Got it on and it's good to go.

[aalvarez04]

Weird, mine also did that. The screw actually popped out though, i bought a new one from mazda for ten dollars. Squirted some pb blaster in and it's fine now. One of the techs said a lot of times they are in there too tight

[sammm]

One of the techs said a lot of times they are in there too tight

That piece just 'floats' in the caliper. It doesn't retract in or out as you adjust the piston.

[Nails]

That's how it's supposed to work but mine was stuck and I broke the splines getting it out so I figured I damaged the others on the piston too.

[SirHustlerEsq]

they're both stuck in my rear brakes. Some rocket surgeon who owned it previously managed to ghetto-up this car as much as possible.